We are continuing to study the immunopathogenesis of human digestive tract cancer by focusing on biological markers produced by benign and malignant mucous membrane. We are improving the clinical use of serial CEA levels as an early index of tumor recurrence and as an indicator for second-look surgery (by adding serial circulating immune complex measurements), as a monitor of therapy and as an index of prognosis. Our studies emphasize the key role of the liver in regulating plasma CEA as well as its clinical significance. We will elucidate the effect of chronic and acute viral hepatitis on CEA levels, both prospectively and retrospectively, and test the hypothesis that non-A, non-B viral hepatitis may be transmitted via CEA-positive transfused blood. We are studying the use of the immunoperoxidase and other immunohistochemical techniques for identifying and localizing CEA and other tumor antigens in tumorous tissues and in body fluids. These methods are useful both for basic understanding and for clinico-pathological use. We will continue to use malignant ascites and pleural effusions as a primary source for new tumor glycoproteins, by identifying, purifying, preparing antibodies to them and developing assays for assessing their clinical usefulness.